DIY Alignments - how flat is flat

[MMiskoe]

So in another post recently about doing alignment on your own, a common thread through many responses was that you have to have a flat floor. So two questions

- how flat is flat?
- how do you check for flatness

I am curious what people consider 'flat' when doing alignments, and how they arrive at that conclusion. I have seen in cataloges nice granite inspection plates (6'x8&#39 which are +/- 0.001" throughout. But since something like that costs about $7500 and weighs 4 tons I doubt too many people are using them for IT car alingments. My shop floor is not like the paddock at Bridgehampton, but it isn't as flat as an inspection grade granite block, so I'm curious where it stands.

Thanks in advance.
Matt

[Andy Bettencourt]

Originally posted by MMiskoe@Sep 25 2005, 08:37 PM
So in another post recently about doing alignment on your own, a common thread through many responses was that you have to have a flat floor. So two questions

- how flat is flat?
- how do you check for flatness

I am curious what people consider 'flat' when doing alignments, and how they arrive at that conclusion. I have seen in cataloges nice granite inspection plates (6'x8&#39 which are +/- 0.001" throughout. But since something like that costs about $7500 and weighs 4 tons I doubt too many people are using them for IT car alingments. My shop floor is not like the paddock at Bridgehampton, but it isn't as flat as an inspection grade granite block, so I'm curious where it stands.

Thanks in advance.
Matt

[snapback]61159[/snapback]

I think the flatness of your area is not that importnat when doing your alignment - obviously, you need something that looks flat AND:

- a camber gauge that you can calibrate to the area your tire is on. You should be close enough like that. Calibrating is key.

Now corner weighting is a whole seperate issue. Using scales with adjustable stands gets you to perfect with about 10 minutes of tweaking with a long 2x4 and a level. Left to right and front to back must be checked.

AB

[lateapex911]

On the scales...

As Andy said, adjustable stands are the easy way to go.

I use a auto laser level once I have found the high point, then adjust up to that point. I use a level on each scale too, just to make things on the same plane.

THe technique using the 2 x 4 and a level is fine, but there are two caveats:
- one, use a nice 3" aluminum extrusion U channel...in place of a 2 x 4...which are known to shrink twist warp and so on.

- and make sure the level is level...many have calibration adjustments, some don't but a little off over 9 feet can add up.

An aside, doing the alignment on the scales is easier thanks to the increased clearance...and the surface is as flat as you'll ever need.

[pfcs]

for alignmrnt or corner weighing, asuming the floor is relatively flat, it is only necc to level the axles. A 4' level is almost long enough to reach from side to side. Establish level ponts for tire contact patches by shimming the low points, frt and rear w/pices of sheet metal, plywood, plexi-whatever is handy, and roll the car onto them, and take your meaurements. Make your adjustments, roll the car back onto your points, and do again. The difference between frt and rear heights is miniscule. Castor readings will be off by the degee (literally) of pitch. A few seconds of a degree? F/R weights will be off slightly too (if frt axle is higher than rear, perhaps a pound will be transferred to the rear). OR- you could spend a lot of money to get fancy stuff you don't really need. What's most important about chassis setup is the integrity, intelligence, and comittment of the guy doing it. also, to the (literal) degree your lateral level is off, so will be your cambers. (if both axles are inclined the same way/same amount) If they're any more incoherent, then don't bother measuring anything. (if you parked the RR tire on a brick, the front cambers would diverge greatly from their settings, even if the front tires were on a level surface. Also-put the driver's weight in the front seat for scaling and alignment. (always for corner wt). Check and record your cambers, remove driver's weight and re-check your cambers. You'll usually see the pass side camber increase a couple tenths. Knowing this, you can do alignments/take measurements/compare apples to oranges in the future with or without having driver's wieght in car

[dickita15]

the advent of cheap laser torpedo levels had made leveling a much easier job. a box of commercial floor tile makes great shims and with a little grease can be used as slip plates as well.

[m glassburner]

I also use cheap plastic floor tiles and a 6ft level I bought at sears hardware store for about 40$ total cost was about 50$ btw a good friend of mine just got back from talledega after helping w/that speed run they did. He has a set of aluminum pads and ramps valued at @1800 $ will sell for @ 1200 @...I know this is'nt the right place to say that.....but revelant :P

[Spinnetti]

Originally posted by MMiskoe@Sep 26 2005, 12:37 AM
So in another post recently about doing alignment on your own, a common thread through many responses was that you have to have a flat floor. So two questions

- how flat is flat?
- how do you check for flatness

I am curious what people consider 'flat' when doing alignments, and how they arrive at that conclusion. I have seen in cataloges nice granite inspection plates (6'x8&#39 which are +/- 0.001" throughout. But since something like that costs about $7500 and weighs 4 tons I doubt too many people are using them for IT car alingments. My shop floor is not like the paddock at Bridgehampton, but it isn't as flat as an inspection grade granite block, so I'm curious where it stands.

Thanks in advance.
Matt

[snapback]61159[/snapback]

Well, best way to find out if all the theories hold water is to align it, then take it to a good shop. IF they match or are close enough, you know your answer.

Another thing you can do is put the level on the floor to check it (I use a 4&#39, then flip it around and check it again - this at least tells you if your level is off.

With a normal garage slab, I've been able to align my IT car right where I wanted it. I've had my work checked twice, and it was right on. IT cars aren't like Formula cars, so given the limited adjustments you can do it just fine. It does take a while tho (I use jack stands and string), and these days I prefer just to have it done to save me time.